The present invention relates to conveyor chain, and, in particular, to a conveyor chain which can convey products at a faster speed than the speed at which the chain is travelling.
U.S. Pat. No. 4,736,834 "Kotegawa" shows a conveyor chain which is intended to be used to carry products at a faster speed than the chain is travelling. It does this by driving the center roller 1, which supports products, with side rollers 2, which ride on tracks. As the chain travels, the side rollers 2 roll along the tracks. The side rollers 2 contact the center roller 1 along their inside diameter and along a side face. This provides good surface contact for driving the center roller 1. However, it also creates a problem.
One of the purposes of this type of chain is that its parts should be able to slip relative to each other in order to accumulate products on the conveyor without creating a high backline pressure. A high backline pressure means that products are pushing against each other with a large force, which tends to damage the products and/or increase the amount of energy needed to drive the conveyor. The large surface area of contact between the side rollers and the center roller, both on side surfaces and inner surfaces, provides for a large friction force between the side rollers and the center roller, which means that this chain can build up a relatively large backline pressure before the center rollers begin to slip relative to their side rollers.